Automatic transmissions of vehicles, such as conventional cars, trucks, heavy equipment, and the like, may be damaged by improper gear changing. Such damage may be severe, in which case the damage is a complete transmission failure caused by a large transmission overstress. On the other hand, transmission damage may be latent, in which case it shows up later as reduced reliability resulting from a series of milder stresses, which are nevertheless greater than the transmission was designed to handle.
The overstresses typically result from a large mismatch between vehicle inertia and engine speed. For example, in one typical improper gear-changing scenario a vehicle's direction is changed by shifting the transmission between forward and reverse gears without first coming to a stop. This scenario requests the transmission to instantly institute an enormous vehicle inertia change. In another typical improper gear-changing scenario, a vehicle's transmission is slammed into gear from a neutral position while an engine operates at a relatively high speed, colloquially referred to as revved up. Again, this scenario requests the transmission to instantly institute an enormous vehicle inertia change so that vehicle speed will thereafter match engine speed.
All vehicles with automatic transmissions potentially face the problem of transmission damage caused by improper gear changing. However, in some vehicles this problem is extremely serious. For example, heavy vehicles, such as trucks and other heavy equipment, are more likely to experience transmission damage due to improper gear changes than other vehicles. The great weight of these vehicles and of the loads which they may carry, when coupled with the great power of the engines which are typically used to propel these vehicles, leads to great potential disparities between vehicle inertia and engine speed. In addition, both heavy and light vehicles suffer increased incidences of transmission damage when they are maintained as part of a fleet, such as a rental or company fleet. Such fleet vehicles are typically driven by persons who are not financially responsible for damage they cause by improperly changing gears. As a result, they tend to be less careful in operating the vehicle's transmissions. Accordingly, those organizations responsible for maintaining a fleet of vehicles, and others having vehicles with automatic transmissions, feel a need for a mechanism or system which prevents such damage.
Prior art devices which address this problem are known. However, the conventional systems are typically configured for incorporation in an overall vehicle design. Hence, they are typically unsuitable for retrofit within existing vehicles. Specifically, such conventional devices are undesirably complicated and expensive when adapted to a retrofit application. While the excessive complication and expense relate both to system components and to component installation, the installation of components is an exceptionally acute problem for fleet operators and others who wish to retrofit existing vehicles. For example, such conventional systems typically require installation of components at difficult-to-access locations within a vehicle, such as under a dashboard or within a transmission. Thus, installation costs are undesirably high.